Distribution and Relative Abundance of Insect Vectors of Xylella fastidiosa in Olive Groves of the Iberian Peninsula.

María Plaza,Carmen Ruz,Jose Pereira,Carmen Capiscol,Susana Sanjuan,José Durán,Manuel Ruiz,Alberto Fereres,Raquel Trillo,Aranzazu Moreno,Daniele Cornara,Marina Morente

doi:10.3390/insects9040175

Abstract

The phytosanitary emergency caused by the spread of Xylella fastidiosa in the Mediterranean has raised demands for a better understanding of the ecology of its presumed and candidate insect vectors. Here, we present the results of a two-year survey carried out in olive groves across southern, eastern and Central Spain and northeastern Portugal. Several sampling methods were tested and compared to select the most appropriate to estimate population levels of potential vectors of X. fastidiosa. The spittlebugs Philaenus spumarius and Neophilaenus campestris (Hemiptera: Aphrophoridae) were the main species associated with olive groves. Both species were widely present on herbaceous ground vegetation within the olive groves; P. spumarius mainly associated with Asteraceae and N. campestris with Poaceae. Due to the patchy distribution of spittlebugs within the olive groves, sweep nets were the most effective and least time-consuming sampling method for the estimation of population size both in the ground cover and tree canopies. Trends in population density showed that spittlebugs can be abundant on ground vegetation but very rare on olive canopies. Spittlebugs disperse in late spring to non-cultivated hosts that act as natural reservoirs. In late fall, adults return to the olive groves for oviposition. However, olive trees may act as transient hosts for spittlebugs and high population densities of these insect vectors should be avoided in areas where X. fastidiosa is present.

Highlights

IntroductionThe vector-borne plant pathogenic bacterium Xylella fastidiosa Wells (1987) affects a great number of economically important crops such as grapes, citrus, olives, and stone fruits among others [1].Originally, the bacterium was thought to be restricted to the Americas, but it has been detected in other continents, i.e., Asia and Europe, likely as a result of human-mediated introductions [2,3,4,5,6,7,8,9]. in South Italy, the bacterium caused a devastating disease named Olive Quick DeclineSyndrome (OQDS), which led to the loss of hundreds of thousands olive trees across the southernmost part of the Apulia region [10]
Additional xylem feeders occasionally found on ground vegetation within and surrounding the olive groves were Lepyronia coleoptrata, collected on Retama sp. plants bordering the grove in Morata de Tajuña in September 2016, and Cercopis intermedia, found on the ground cover in
The spittlebugs Philaenus spumarius and Neophilaenus campestris (Hemiptera: Aphrophoridae) were the main species of xylem feeders associated with olive groves

Summary

Introduction

The vector-borne plant pathogenic bacterium Xylella fastidiosa Wells (1987) affects a great number of economically important crops such as grapes, citrus, olives, and stone fruits among others [1].Originally, the bacterium was thought to be restricted to the Americas, but it has been detected in other continents, i.e., Asia and Europe, likely as a result of human-mediated introductions [2,3,4,5,6,7,8,9]. in South Italy, the bacterium caused a devastating disease named Olive Quick DeclineSyndrome (OQDS), which led to the loss of hundreds of thousands olive trees across the southernmost part of the Apulia region [10]. The first detection of X. fastidiosa occurred in the Balearic Islands in 2016 in three cherry trees reared in a nursery This finding promoted and intensified field surveys, which revealed the presence of the subspecies multiplex, fastidiosa and pauca spread throughout the archipelago except for Formentera Island. This bacterium subspecies complex affects economically important crops such as olives, almonds and grapes among others [11]. In June 2017 X. fastidiosa was detected for the first time in the Iberian Peninsula, in el Valle de Guadalest (Alicante), eastern Spain, in almond trees In this case the subspecies multiplex was identified. Olive trees infected by X. fastidiosa subspecies multiplex were detected in Madrid (Central Spain)

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Discussion

Conclusion